小麦芽脂肪酶酶学性质以及制麦过程的酶活变化

Characterization of wheat malt Lipase in malting

以对硝基苯酚丁酸酯为底物,确定了小麦芽脂肪酶的酶学性质:最适温度为37℃;最适pH为8.0;4～35℃脂肪酶的热稳定性较好,35℃下保温60 min后其活力仍可保持在88.37%,45℃保温60 min后其活力保持在46.81%,55℃保温60 min酶失活;pH5.5～6.0范围内对脂肪酶的破坏力相对较小,保温60 min其活力仍可分别保持在95.11%和91.11%;Fe3+对脂肪酶有较强的抑制作用;Cu2+、Mn2+、Al3+对脂肪酶的抑制作用较小;Ca2+、EDTA对脂肪酶有较强的激活作用。小麦制麦过程中发芽第4天酶活达到最大值,为8.52 u/g,随后酶活下降;干燥会破坏部分脂肪酶的酶活,损失率为27.06%。小麦芽籽粒、胚芽、胚根中的脂肪酶酶活依次降低,分别为8.01 u/g、7.55 u/g、6.83 u/g;协定法麦汁糖化过程中,无胚芽麦芽脂肪酶的酶活比有胚芽的低,且酶的失活速度也比较大,在55 min(70℃)时,脂肪酶完全失活。

Taking p-nitro phenol butyrate as substrate,enzymatic properties of Lipase in wheat malt were confirmed as follows： optimal temperature was 37 ℃;optimal pH was 8.0;thermal stability of Lipase was good at 4～35 ℃,and it still kept 88.37% and 46.81% of activity when it was correspondingly incubated at 35 ℃ and 45℃for 60min.When it was incubated at 45℃ for 60min,the enzyme was inactive.Its activity could be kept 95.5% and 91.11% when it was incubated at pH 5.5 and 6.0 for 60min.Fe3＋ can strongly inhibit the activity of Lipase.EDTA had an obvious activation on Lipase.During germination,the activity of the enzyme reached a maximum of 8.52u/g on the fourth day,and then decreased.The activity of the enzyme in kernel,embryo,radical decreased in turn,which respectively were 8.01 u/g,7.55 u/g,and 6.83u/g.During EBC mashing,the activity of the enzyme in malt without embryo was lower than that in malt,and the inactivation rate was more quickly.Lipase was inactive completely at 70℃ for 55min.